METHOD FOR IMPROVING THE RHEOLOGY AND THE PROCESSABILITY OF CELLULOSE-BASED SPINNING SOLUTIONS

Abstract: The invention relates to the addition of an alkoxylate having the formula (I) X(NX-R)nNX2 and/or an alkoxylate having formula (II) wherein X is hydrogen, the group R1CO-, in which R1 is a hydrocarbon group having 7-23 carbon atoms or the group -(B)mH, in which B is an alkyleneoxy group having 2-4 carbon atoms and m is 1-7, provided the number of groups of formula R1CO is 1 or 2 and the total number of B is 2-20, R is an alkylen group having 2-3 carbon atoms and n is 2-10, preferably 3-7, to improve the rheology and the processability of a cellulose-based spinning solution.

Description: METHOD FOP IMPROVING THE RHEOLOGY AND THE PROCESSABILI- TY OF CELLULOSE-BASED SPINNING SOLUTIONS The present invention relates to a method for imp¬ roving the processability and the rheological properties of cellulose-based spinning solutions by adding an alkoxylated amine compound. The cellulose content of the spinning solution and/or the flow rate thereof through piping, pumps, filters and spinning nozzles can thus be increased, resulting in improved processability, economy and product properties. It is known that the rheology of cellulose-based spinning solutions exhibits different phases of state at varying shear forces. In Gδtze Chemiefasern, p. 499, there is thus given an example in which a cellulose- based spinning solution exhibits high structural visco¬ sity in rest, while the apparent viscosity changes at varying shear forces. During the passage through a spin¬ ning nozzle, the viscosity is reduced by up to about 1/50 of the viscosity in rest. The apparent viscosity can also be increased by increasing the content of cel¬ lulose in the spinning solution. The viscosity increase entails many drawbacks. For example, it has been found difficult to use cellulose xanthate solutions having a cellulose content above 10% by weight, if regenerated cellulose fibres having high strength and extension are to be obtained. Other ways of increasing the apparent viscosity is to increase the average polymerisation degree of the cellulose solutions, to change the ratio of cellulose content to liquor content or to lower the temperature of the cellulose solution. US Patent Specification 4,418,026 proposes adding as solvent to a cellulose acetate a composition contain¬ ing polyethylene glycol having a molecular weight of 100,000-1,000,000. The purpose is to dispense with the different purification stages which are generally requi¬ red after the acetate has been formed by acetylation, when using conventional cellulose acetate solvents. From Swedish Patent Specification 8405800-7 it is known to improve the processability of cellulose-based spinning solutions by adding an ethylene oxide adduct having a molecular weight of 1.1-4.5 million, whereby the flow rate of the cellulose-based spinning solution through the spinning nozzle can be considerably in- creased. Even if high-molecular-weight ethylene oxide adducts have a good effect and significantly reduce the apparent viscosity of cellulose-based spinning solu¬ tions, their use has been hampered by the fact that they are difficult to produce and, hence, involve high costs. There is thus a need for other additives that can re¬ place the high-molecular-weight polyethylene oxide adducts and also contribute to improved reactivity, reduced gel particle formation and improved filterabi- lity. According to the present invention, it has now been found possible to obtain the desired rheological changes in cellulose-based spinning solutions and, for example, at a constant pressure drop over a spinning nozzle havi¬ ng conventional conical holes, to increase the flow rate of the cellulose-based spinning solution by adding an alkoxylate having the formula X(NX-R) n _NX 2 (I) and/or R(NX-R) n _2NX 2 wherein X is hydrogen, the group R]_CO-, in which R]_ is a hydrocarbon group having 7-23 carbon atoms or the group -(B) m H, in which B is an alkyleneoxy group having 2-4 carbon atoms and m is 1-7, provided the number of groups of formula Rτ_CO is 1 or 2 and the total number of ' B is 2-20, ?. is a alkylene group having 2-3 carbon atoms and n is 2-10, preferably 3-7. Preferably, R]_ is a straight or branched, saturated or unsaturated aliphatic group having 9-21 carbon atoms. Of the total number of alkyleneoxy groups, 50-100% are suitably ethyleneoxy groups while the remaining alkyleneoxy groups preferably are propyleneoxy groups or a mixture of propyleneoxy groups and butyleneoxy groups. The total number of alkyleneoxy groups usually is 3-15, preferably con¬ sisting entirely of ethyleneoxy groups. The alkoxylate according to formulae I and II may in principle be added at any time during the production of the cellulose-based spinning solution. For example, the alkoxylate can be sprayeό on tc the native cellulose and/or be added to the mercerising liquor, to the solvent and/or to the finished spinning solution. If desired, it is possible, in addition to the alkoxylate of formula (I), to add also other alkoxylates and/or solubilising agents. One example of such an addi¬ tive is a compound having the formula X 1 (NX 1 -R) n N(X 1 )2 (HI) wherein R and n are as defined above and χl is hydrogen or the group (B) m H, where B and m are as defined above, the total number of B being 2-20. Compounds of formula (III) can suitably be added in an amount of 0-70% by weight of compounds of formula (I) . Other examples of supplementary additives are fatty amine ethoxylate, polyethylene glycols having a molecular weight of 400-10,000, phenol and aliphatic alcohols as well as their alkoxylates, and ethoxylated glycerol. The alkoxylate according to formula (I) or (II) also has a favourable effect on the filterability of the cellulose-based spinning solution in that the number of gel particles in the solution is reduced, so that less interference is caused during its flow through the spin- ning nozzle. The adducts also have a modifying effect by reducing the regeneration speed of the cellulose-based spinning solution when emerging from the spinning nozzle into the pricipitating bath. This results in improved thread strength and thread extension, at the same time as the improved regeneration of the cellulose-based spinning solution enables increased cellulose content and/or increased spinning speed. One way of obtaining compound (I) or (II) is to react a carboxylic acid having the formula RlCOOH (IV) wherein R_ is as defined above, with a polyalkyleneamine having the formula H':TH-R) n NH2 (V) wherein R and n are as defined above, in a molar ratio of 0.5-2, preferably 0.9-1.3 of carboxylic acid to poly¬ alkyleneamine, whereupon the reaction product is alkoxy- lated with 2-20 moles per mole of polyalkyleneamine of formula (V) . After the reaction between the carboxylic acid and the polyalkyleneamine and subsequent alkoxyla- tion, there is obtained an alkoxylate of formulae (I) and/or (II) . In the aqueous environment prevailing in conventional cellulose-based spinning solutions, the alkoxylate of formula (II) is however hydrolysed and forms an alkoxylate of formula (I) . If carboxylic acid is used in excess, a condensate is obtained having more than one hydrocarbon group per polyethyleneamine, whereas if there is a deficiency of carboxylic acid or it is present in equimolar amounts, a certain amount of unreacted polyalkyleneamine will remain in the reaction mixture, which in the subsequent alkoxylation forms com¬ pounds of formula (III) . The alkoxylate of formulae (I) and (II) can be added within wide limits, but the amount usually is above 0.1 kg/tonne of cellulose, preferably above 1 kg/tonne of cellulose. For economic and techni- cal reasons, the added amount suitably is below 40, pre¬ ferably 20 kg/tonne of pulp. Thanks tc the invention, it is possible to change the rheology of the spinning solution to optimise the flow conditions in the process. For example, the cellu¬ lose content of the spinning solution can be raised, the cellulose-to-liqour ratio of the spinning solution can be optimised, and the average polymerisation degree of the cellulose in the spinning solution can be increased, thus increasing the degree of orientation of the fibres which are formed in the spinning nozzle. Such fibrers exhibit higher strength and a more uniform thickness. An alternative to increasing the content of cellulose is to increase the flow velocity of t e spinning solution in the nozzle. The invention is especially useful for cellulose xanthate and copper/ammonium cellulose, but it can also be used for other cellulose-based spinning solutions, such as cellulose carbamate, cellulose dissolved in a tertiary amine oxide or in cold sodium hydroxide. The invention will be further illustrated by the following Examples. EXAMPLE 1 An ethoxylate of a fatty-acid polyamine adduct obtained by reacting 1.1 mole of fatty acid and 1 mole of polyethyleneamine, followed by ethoxylation with 5 moles of ethyleneoxide, was added to a spinning solution of cellulose dissolved in copper ammonium. The copper ammonium cellulose had been produced from a mixture of 8.5% NH3 and 4% Cu in the form of Cu(OH)2, based on the weight of the cellulose, in water of 22°C. The resulting spinning solution contained 10.0% copper ammonium cellu¬ lose calculated as pure cellulose and 2% Na2Sθ4 calculated as pure cellulose. After filtering, the rheo- logical properties of the copper ammonium compound were examined. Measurements were conducted in a viscometer of the make Brookfield. TABLE 1 These results show that an addition of 1-4 kg of the ethoxylate per tonne of copper ammonium cellulose gives a viscosity reduction in the order of 50%. EXAMPLE 2 The same spinning solution and the same ethoxylate as in Example 1 were used, but the ethoxylate was added in other amounts. Spinning solutions with and without additions according to the invention were tested for flow rate through a spinning nozzle having 80 conical 200 μm-diameter holes at varying pressure drops. The following results were obtained. Table 2 Spinning flow rate (mg/sec) and increase (%) Pressure Without With kg/cm-2 Increase With Increase additive additive additive Q. Q. 0.3 kg/tonne O 1.5 kg/tonne O 1 82 97 +18 155 +89 2 240 363 +51 770 +221 3 468 570 +22 1462 +212 From these results appears that the spinning flow rate increases significantly by the addition of the ethoxylate. EXAMPLE 3 A peroxide-bleached sulphite cellulose having an -cellulose content of 92% by weight was mercerised in liquor containing 18.2% by weight of NaOH at 45°C. The alkali cellulose was xanthated with 30.5% by weight of C≤2 based on the weight of the cellulose. The finished spinning solution contained 10.1% by weight of cellulose xanthate and 5.4% by weight of NaOH. The falling-ball time was 55 sec. To this cellulose solution was added 0, 5, 15 or 30 kg/tonne of the ethoxylate in Example 1, and the flow rate of the different spinning solutions passing through a spinning nozzle having 150 holes of a diameter of 60 μm at a pressure of 2, 3 and 4 kg/cm 2 out into an aqueous solution containing 17% by weight of NaOH was measured. The following results were obtained. Table 3 From these results appears that the flow rate through the spinning nozzle increases significantly by the addition of the ethoxylate. EXAMPLE 4 The same spinning solution as in Example 3 was admixed with 5 kg of the ethoxylate in Example 3. The cellulose solution was pumped through a spinning nozzle having 250 holes of a diameter of 60 μm into a regenera¬ tion bath. This bath was composed of 150 g H2SO4, 10 g ZnSθ4 and 300 g Na2S0 per litre of spinning bath and had a temperature of 50°C. The partly regenerated fibre was stretched in a stretching batn at 90°C, washed and dried. Spinning speed was 47.5 m/min. The strength and the extension of the fibres were determined in dry state in a Textechno Fafegraph accord¬ ing to BISFA standards, and the tensile energy absorp¬ tion was determined as the product of strength and extension. The wet modulus of the fibres was also deter¬ mined in the same apparatus. For comparison, the same tests were performed on fibres obtained from the same spinning solution, but without the addition of the ethoxylate according to Example 3. The following results were obtained. Table 4 Fibre properties Addition kg/tonne 0 5 Fibre coarseness Dtex g/lOOOm 2.01 2.05 % increase - + 2.0 Tensile energy absorption 39.7 44.1 (strength x extension) Increase % - + 11.1 Wet modulus, cN/dtex per 5% exten¬ 0.151 0.183 sion Increase % - 20.8 From these results appears that the addition of ethoxylate gives an improvement of the physical proper- ties of the fibres. EXAMPLE 5 A cellulose solution was prepared from chlorine- bleached spruce sulphite pulp in the same way as in Example 3. The spinning solution contained 10.2% by weight of cellulose xanthate and 5.8% by weight of NaOH and had a falling-ball time of 60 sec. Cellulose solu- tions with the addition of 0.5 and 15 kg of the ethoxy¬ late in Example 1 were tested for spinning flow rate un¬ der the same conditions as in Example 3. The following results were obtained. Table 5 From these results appears that the addition of ethoxylate increases the flow rate through the spinning nozzle. EXAMPLE 6 The cellulose solution of Example 5 was subjected to a spinning test in respect of fibre size and tensile energy absorption under the same conditions as in Example 4, but with the exception that the spinning speed was 87 m/min. The following results were obtained. Table 6 Addition Fibre coarseness Tensile energy absoprtion kg/tonne Dtex Increase % Strength x extension Increase % 0 2 . 15 37.0 5 2 . 74 +28 . 1 40. 1 +8 . 4 From these results appears that both the fibre coarseness, i.e. the flow rate through the spinning nozzle, and the tensile energy absorption increase in the presence of the ethoxylate in the spinning solution.

Claims: CLAIMS 1. A method for improving the rnεology and the processability of a cellulose-based spinning solution, c h a r a c t e r i s e d in that an alkoxylate having the formula X(NX-R) n NX 2 (I) and/or an alkoxylate having the formula wherein X is hydrogen, the group R1CO-, in which R ] _ is a hydrocarbon group having 7-23 carbon atoms or the group -(B) H, in which E is an alkyleneoxy group having 2-4 carbon atoms and m is 1-7, provided the number of groups of formula R_C0 is 1 or 2 and the total number of B is 2-20, R is an alkylene group having 2-3 carbon atoms and n is 2-10, preferably 3-7, is incorporated in the spin- ning solution. 2. A method as claimed in claim 1, c h a r a c t e r i s e d in that the number of alkyleneoxy groups is 3-15. 3. A method as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the alkyleneoxy groups are ethyleneoxy groups. 4. A method as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that R]_ is a straight or branched, saturated or unsaturated aliphatic group. 5. A method as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the spinning solution is a cellulose xanthate solution or a copper/ammonium cellulose solution. 6. A method as claimed in any one of claims 1-5, c h a r a c t e r i s e d in that the alkoxylate of formulae (I) and (II) is added in an amount of 0.1-40, preferably 1-20 kg/tonne of cellulosa in the spinning solution. 7. The use of an alkoxylate having the formula X(NX-R) n NX 2 (I) and/or an alkoxylate having the formula wherein X is hydrogen, the group R_CO-, in which R- j _ is a hydrocarbon group having 7-23 carbon atoms or the group -(B) m H, in which B is an alkyleneoxy group having 2-4 carbon atoms and m is 1-7, provided the number of groups of formula R-]_C0 is 1 or 2 and the total number of B is 2-20, R is an alkylene group having 2-3 carbon atoms and n is 2-10, preferably 3-7, to improve the rheology and the processability of cellulose-based spinning solu¬ tions. 8. Use as claimed in claim 7, c h a r a c t e r i s e d in that the number of alkyleneoxy groups is 3-15. 9. Use as claimed in claim 7 or 8, c h a r a c t e r i s e d in that the alkyleneoxy groups are ethyleneoxy groups. 10. Use as claimed in claim 7, 8 or 9, c h a r a c t e r i s e d in that R]_ is a straight or branched, saturated or unsaturated aliphatic group.

Inventors: SOEDERLUND CARL-AXEL, STRANDBERG MARGRETH, UNEBACK INGMAR, SOEDERLUND, CARL-AXEL, STRANDBERG, MARGRETH, UNEBACK, INGMAR
Applicants: BEROL NOBEL AB, SOEDERLUND CARL AXEL, STRANDBERG MARGRETH, UNEBACK INGMAR, SOEDERLUND, CARL-AXEL, STRANDBERG, MARGRETH, UNEBACK, INGMAR
Application year: 1994
Main classification: D01F2
IPC codes: C08G2, C08L1, D01F2